1. Field of Invention
The present invention relates to graphics display systems and more particularly to graphics display systems that employ parallel processing. The invention relates to the process for identifying or picking a displayed object from a graphics display for further processing, and in particular, to the process for identifying the selected object during parallel generation of a display image.
2. Description of Related Art
The problem of graphics object selection, or picking, is well known in the art of graphics display systems. Graphics display systems are used in computer-aided design (CAD) to represent mechanical drawings and resulting manufactured objects. Graphics display systems may also be employed for simulation purposes, including the use in aircraft, automobile, and military vehicle pilot or driver training devices. The operator of a CAD system or developer of a simulator environment must provide the graphics instructions necessary to generate the required object on the graphics display screen. Displayed objects are then available for manipulation, modification, and deletion. The operator must have some method for communicating to the display system which of the displayed objects is being selected for manipulation.
Prior art systems provide several methods for communicating between the operator and the graphics display system. For example, Foley and Van Dam in Fundamentals of Interactive Computer Graphics, Addison-Wesley Publishing Co., 1982, pp. 165-168, describe a pick identification process where a display processing unit (DPU) detects a light pen selection of the graphics object and communicates the name of a segment being drawn to the graphics controller. Foley and Van Dam also describe other pick schemes in the referenced material.
U.S. application Ser. No. 07/043,019, now U.S. Pat. No. 4,847,605, filed Apr. 27, 1987 entitled "Picking in a Graphics System", commonly assigned, describes the coordination between a picking window and the display generator. U.S. Pat. No. 4,451,895 to Sliwkowski, describes the process of picking and address correlation in a graphics display system. Each of these references describes a means and method for detecting which segment of a graphics object is referenced during an operator initiated pick request. Each of the references provides a means for comparing the location of the pick window or pick selection point to the graphics object. In each of these cases it is assumed that the graphics object is being generated one point at a time. The picking function in the above references either tests each individual point as it is generated, or compares the address of the pick window to the addresses of the segments in display memory. None of these references address the problem of picking in a parallel processing environment where a number of pixels may be generated for display in parallel. The present invention is directed to solving the pick problem in the parallel processing environment.